86 3/4 ton carb problem?


Junior Member
Hi guys I need your advice on a problem I am having with my truck. This past fall I bought a 1986 chevy 3/4 ton as a backup plow truck. The exhaust was rusted away where the manifolds met up to the pipes so the next day I had a guy put on new flanges and some new pipe to close it up. When I got the truck back I noticed that he had cut off some sort of "collector" that came off both exhaust manifolds and joined together. (Looks like it is some sort of emissions thing) He welded up the holes left in the manifolds from this now missing piece. When I stated driving the truck on a normal basis I noticed that It would not shut off properly it would "diesel". I also noticed it wouldnt pull a hill by my house it felt like it was loaded up. I put new plugs, wires, cap and rotor on which helped for a little while. Then I noticed that when coming up to a stop sign that it would be stuck on a high idle and I woud have to kick it down. The first snow I used it to plow with and I dropped the front end over a six inch ledge and the truck didn't have enough power to pull itself back over. I had to put it in low range to get back over the ledge. It got to the point where the truck wouldn't stay running and I had to switch vehicles to finish my route. I changed the fuel filter after that but it didn't help either. Some people have suggested the timing jumped. I thought maybe getting rid of that collector thing and welding up those holes made the jetting too rich but nobody thinks that mattered. Any Ideas? Sorry for the long post.



Senior Member
Glenview, Ill.
Neal; I don't think that by removing the emission air tubes caused your truck to loose power, all he did was to stop air from the "air pump" from being added to the exhaust to control emissions. (Did he tell you this was just to stop an exhaust leak and to prevent a possible fire and you would need to have them replaced? It's illegal to remove or dissable any emission control device) You need to check and see if any of the vacuum lines to the valves that controled the air pump management and EGR valve were disconnected or rerouted. Check the timing and see if it meets specs. Hopefully there is still a diagram for all the vacuum routing and timing info still under the hood. Hope you get it running again. John

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